Traversing gear arrangement for a crane moving on rubber tired wheels or the like

ABSTRACT

The invention relates to a traversing gear arrangement for a crane moving on rubber-tired wheels or the like. The crane having an electric motor functioning as the traversing gear and including gearing and wheels arranged in pairs. The wheels in each of the pairs of wheels are connected to each other by a hollow pipe shaft such that one of the wheels is a drive wheel, while the other is a free wheel. The traversing gear connected to the drive wheel is mounted inside the pipe shaft.

The invention relates to a traversing gear arrangement for a cranemoving on rubber-tired wheels or the like.

BACKGROUND OF THE INVENTION

In prior art, a sub-chassis of a crane moving on rubber-tired wheelscomprises two large wheels one after the other, and the wheels can beturned to be parallel for lateral movement. The turning is conducted byturning the wheels to the same direction with a hydraulic cylinder oraggregate in a place specifically reserved for turning, e.g. on a marbleslab. Another possibility is to lift the wheels from the ground for theduration of the turning action. Instead of two large wheels, thesub-chassis may comprise a pair of small wheels, both of which are drivewheels. In the traversing movement, power transmission is usuallyimplemented by open gearing with chain gears and transmission chains.

U.S. Pat. Nos. 3,280,931 and 3,645,406 teach a solution in which asub-chassis of a crane comprises two parallel wheels that are both drivewheels. The pair of wheels is turned with a separate turning gear. Thedisadvantage of the prior art arrangement is that turning is difficult.Further, because of the hydraulic equipment and chain gearing, manycomponents are needed, and so there are many points that may needservicing or that may leak. Chain gearing, implemented as open gearing,extends at least partly beyond the wheelwork and thereby requires a lotof space and, since it is not sufficiently protected against minorbumps, may be easily damaged.

SUMMARY OF THE INVENTION

The object of the present invention is to overcome the abovedisadvantages and to provide a new and advantageous solution for atraversing gear arrangement of a crane moving on rubber-tired wheels orthe like. Embodiments of the invention are characterized by what is setforth in the other claims.

An advantage of the invention is that the traversing gear will beprotected inside a pair of wheels. The gear casing is small and compact:no parts extend beyond the tires. Because there are few components,little servicing is needed. Another advantage is that the wheels can beturned without any additional apparatus, such as hydraulic equipment,and the turning can be performed anywhere. Yet another advantage is thatthe wheels can be turned steplessly, so it is possible to move the cranediagonally or in a circle. Also, the turning does not wear the tiresnotably.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail bymeans of one embodiment with reference to the attached drawings, inwhich

FIG. 1 shows a diagonal top view of a crane,

FIG. 2 shows a shaft arrangement in one pair of wheels on a sub-chassisin the longitudinal direction of the sub-chassis, and

FIG. 3 shows a partly cross-sectional side view of a pipe shaft in onepair of wheels.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a crane 1 in which the invention is used, four sub-chassisassemblies 3 being fitted on two lower beams 2 of the frame structure atthe lower corners of the crane. Each sub-chassis comprises two pairs ofwheels 4 mounted in the middle of the horizontal shaft between the pairof wheels on vertical pipes 5 located at the ends of the sub-chassissuch that they pivot about the vertical axis of the vertical pipe 5. Thecrane is also provided with a diesel generator 6, which supplies thecrane with power, and a electric distribution unit 7. The traversinggear of the crane, which is not shown in FIG. 1, is arranged inconnection with the pairs of wheels 4 and comprises e.g. a secondaryshaft 19, gearing 16, an electric motor 28, and a brake 29 affecting theshaft of the electric motor.

FIG. 2 shows the structure in greater detail. At both ends of thesub-chassis, a vertical pipe 5 extends downward from the sub-chassis;the pipe is hollow, and expands conically on the inside toward thebottom. At the upper end of the conical expansion there is a space for abearing 10, and at the lower end of the expansion there is a space for alower bearing 12. Each pair of wheels 4 is mounted on a conical hole inthe vertical pipe to pivot about the vertical axis of the hole by meansof a king pin 8, which comprises an upper cylindrical bearing area 9 forbearing 10 and a lower cylindrical bearing area 11 for bearing 12. Thepart of the king pin between the bearing areas narrows conically towardthe top, and so the diameter of bearing area 9 is smaller than that ofbearing area 11. Immediately below bearing area 11, the king pin furthercomprises a cylindrical flange 13, whose diameter is greater than thatof bearing area 11. The flange provides a supporting surface for bearing12, and the king pin is fastened at this flange to a pipe shaft 17between wheels 4a and 4b of the pairs of wheels 4 with fastening bolts27.

At the lower end of the vertical pipe 5 there is also a locking device,such as a band brake 15, affecting the lower end of the vertical pipeand the flange 13 of the king pin 8, the locking device beingspringdrivenly pressed against the lower end of the vertical pipe andthe perimeter of the flange as the brake is in the hold position. Thebrake is released by means of a spindle motor (not shown in the figs.)or the like as the wheels are turned. Between the flange 13 and thelower end of the vertical pipe there is also a packing 14 that preventsthe lubricant of the bearing from coming into contact with the brakingarea of the band brake.

Both wheels of the pair of wheels 4 are mounted on a pipe shaft 17connecting the wheels by means of cylindrical roller bearings 23 and 24arranged on a bearing area specifically provided on the pipe shaft. Theinnermost bearing 23 extends inward in the axial direction to a shoulder31 that is adjacent to the bearing area of the pipe shaft. On the sideof the free wheel 4b, the innermost bearing 23 is axially locked by anabutment ring 26 for the rim of the wheel, and on the side of the drivewheel 4a, by an abutment ring 18 for the rim of the drive wheel. Theoutermost bearing 24, in turn, is axially locked on the side of thedrive wheel 4a by the abutment ring 18 for the rim of the drive wheeland by a ring-shaped flange 22 fastened to the pipe shaft, and on theside of the free wheel 4b, by the abutment ring 26 for the rim and by aring-shaped flange 30 fastened to the pipe shaft.

The abutment ring 18 for the rim of the drive wheel 4a in a pair ofwheels 4 is part of the rim beyond which part of the abutment ring 18extends, forming a cup-shaped part lying on its cylindrical surface withits bottom in an essentially vertical position. In the middle of the cupbottom there is a toothed 20 hole that fits into the toothed end of thesecondary shaft 19. Power is transmitted from a traversing motor 28through gearing 16 to the drive wheel via the toothing of the abutmentring 18. The toothing is protected by a cover 21, which is fastened tothe bottom of the cup of the abutment ring by means of screws.

The pipe shaft 17 forms a frame for the entire system of pairs ofwheels. The pipe shaft protects the traversing gear against damage,functions as a bearing area, a gear casing, a cooling tunnel for themotor and a supporting surface 35 for the king pin 8 functioning as theturning bearing. Seen from the lateral side, the pipe shaft issymmetrical and has on the upper surface in the middle of the pipe shafta short upward-opening pipe branch 34 whose upper surface 35 is providedat symmetrical intervals with threaded holes for the fastening bolts 27,with which the king pin 8 is fastened to the pipe shaft 17. In addition,the ends of the pipe shaft are provided with threaded holes forfastening the flanges 22 and 30 by means of screws.

The hollow interior of the pipe shaft is sufficiently large toaccommodate the gearing 16 and the motor 28 and brakes 29 of thetraversing gear. One end of the gearing is fastened to the pipe shaft bya ring-shaped flange 22 with screws 37. The ring-shaped flange 22 may bea separate flange, whereby it must also be fixed separately to the gearcasing, or it may be an integral part of the gear casing, as shown inFIG. 2. Between the flange 22 and the secondary shaft 19 there is apacking 36. The countertorque of the torque affecting the wheels issupplied to the pipe shaft 17 with the flange 22 and fixing screws 37,i.e. the gear is prohibited from rotating in relation to the pipe shaft.Further, the gearing is supported on the inside of the pipe shaft by anabutment ring 25. The electric motor inside the pipe shaft operating asa traversing motor is fastened to the other end of the gearing. The pipeshaft also comprises at least two vent holes 7--one on each side--forthroughflow of the cooling air. The cooling air is input through thecenter hole of the ring-shaped flange 30 from that end of the pipe shaftwhich is on the side of the free wheel 4b e.g. by means of a fan (notshown in the figure) that is positioned behind the brake, and outputthrough the vent holes past the brake and motor.

The traversing gear arrangement of the invention makes it possible toturn the direction of travel of the crane in the following manner:Usually, when a crane is steered to the lateral direction, the pairs ofwheels 4 on the sub-chassis 3 are one after the other in thelongitudinal direction of the sub-chassis. The band brake 15 functioningas a locking device is locked and although only wheels 4a are drivewheels, the crane moves in a straight line thanks to the locking effectof the band brake. If one wants to change the direction of travel, theband brake 15 is released, whereby the pair of wheels is able to turnabout the symmetrically positioned vertical axis of the pair, thevertical axis coinciding with the vertical axis of the vertical pipe 5at the end of the sub-chassis and with the vertical axis of revolutionof the king pin 8. A turning action takes place since only one of thewheels in the pair of wheels is a drive wheel, while the other is a freewheel. At one end, the pairs of wheels on both sub-chassis assembliesare arranged to turn simultaneously to opposite directions as the craneis turned, whereby the forces caused by the turning action are reversedand the crane remains stationary. After the turning, the band brake 15is locked and the crane is ready to be steered to the new direction. Theturning action is performed by the traversing gear of the crane, whichcomprises e.g. the above-mentioned electric motor 28 and gearing 16.

The driving and turning action of the crane are implemented by PLCcontrol. The secondary shaft 19 comprises a pulse detector arrangement,which calculates the turning angle of the secondary shaft, starting froma specified zeroing point. The pulse calculation information is suppliedto a control circuit, which forwards it to the electric motor 28. Thecalculation conducted by the pulse detector arrangement shows theturning angle of the wheels, and the wheels can also be adjusted to adesired angle by this arrangement. In the positions for lateral traveland longitudinal travel the pulse detector arrangement comprises extracontrol limits that are 90 degrees apart. At the control limits, thepulse detector information is zeroed, so that the system will alwaysknow the position of the wheels.

It will be obvious to one skilled in the art that the differentembodiments of the invention are not limited to the example describedabove but may vary within the scope of the attached claims. For example,some part of the traversing gear may thus be located either fully orpartly outside the pipe shaft.

I claim:
 1. A wheel traversing gear assembly for a crane moveable onwheels comprising a hollow pipe shaft,a pair of wheels, each of thewheels being mounted on the pipe shaft, one of the pair of wheels beinga drive wheel and the other a free wheel, a traversing gear including anelectric motor and gearing, the traversing gear being connected to thedrive wheel and at least partly disposed inside the pipe shaft, andfirst and second bearings arranged to roll on a surface of the pipeshaft, the drive wheel being mounted on the pipe shaft via said firstroller bearing and the free wheel being mounted on the pipe shaft viasaid second roller bearing.
 2. The assembly according to claim 1,wherein the drive wheel and the free wheel are mounted at opposite endsof the pipe shaft.
 3. The assembly according to claim 2, wherein thepipe shaft is arranged to function as an air guide for the electricmotor.
 4. The assembly according to claim 1, wherein the pipe shaft isarranged to function as an air guide for the electric motor.